Suppose that sometime this year two US airliners find themselves on a collision course. An air traffic controller relying on rapidly deteriorating 1960s-vintage equipment must distinguish the two planes from others on his radar screen and make a mental calculation about the likelihood of a crash. Though his radar display is two-dimensional, the controller must envision the planes' flight paths in three dimensions, then project the paths through time. He must take into account that, say, one plane is turning sharply and rapidly descending, while the other is slowly climbing. Alarmed, he'll quickly get on his radio to instruct one of the pilots to change course. Only if his message isn't garbled or drowned out or misunderstood will an accident be averted.

Now imagine the same scenario 15 years from now. Both planes carry satellite-based navigational equipment that identifies their positions with a precision far outstripping radar's. Instead of passing information by voice, pilots rely on digital communications gear that automatically transmits a constant flow of data about the planes' location, direction, and speed to controllers and other nearby aircraft. Surveillance and data processing equipment on the ground and aboard the aircraft projects the planes' flight paths over time, instantaneously making the same calculations that the 1996 controller struggled to do in his head. Long before the two aircraft seriously threaten each other, cockpit displays in both planes warn the pilots of the potential conflict and recommend course changes.

Welcome to "free flight," the aviation community's term for changes that constitute the most significant development in air traffic management since the invention of radar 60 years ago. Under free flight, many tasks now carried out by air traffic controllers will be automated, and some of the authority that controllers possess will be shifted to pilots. Not surprisingly, the engine driving free flight is digital technology, which has laid bare the obsolescence of the current air traffic control system.

"It's as though our telephone systems were still operating with manual switchboards, with telephone operators who were pulling the plugs out of one outlet and putting them in another," says James Coyne, president of the National Air Transportation Association, which represents airport businesses such as food vendors and repair services. "All of the information that flows to and from a pilot today in virtually all aircraft is done on a strictly single-voice channel, back and forth, with human beings actually saying all the words live. As anyone can imagine, that is an extremely inefficient way to convey data."

Free flight mirrors the shift from centralized mainframe technology to distributed, networked systems that's occurring in many realms. And, as in those arenas, the shift faces considerable obstacles, most notably cost. The Federal Aviation Administration, which oversees the US air traffic control system, has embraced the concept but may have a hard time persuading Congress to allocate the many billions of dollars that free flight will probably cost. Thanks to past debacles in developing air traffic management technology, the FAA's credibility is notoriously low, to the point that proposals for privatizing the agency are filtering through Congress.

Nevertheless, most discussion of free flight has a tone of inevitability, chiefly because it makes so much sense. Though free flight restores to pilots some of the same freedom to choose routes, altitudes, and speeds that aviators enjoyed before the advent of air traffic control in the mid 1930s, what drives it is not some romantic notion of airborne adventure, but economics. Pilots no longer required to follow rigid routes presumably would fly more direct paths to their destinations, saving fuel and increasing airline productivity. It's not surprising that free flight's strongest advocates are the nation's major air carriers, which maintain that free flight would enable the industry to recoup a significant portion of the US$3.5 billion it claims to lose each year because of limitations in the current air traffic control system. Since the industry only recently returned to minimal profitability after losing as much as $12.8 billion between 1990 and 1994, it's possible that free flight could make the difference for some carriers between lucrative and losing
years.

Contributing writer Jacques Leslie (jacques@well.com) is the author of The Mark: A War Correspondent's Memoir of Vietnam and Cambodia.